The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XII. Unanchored Forked Stream in the Propagating Path of a Protostellar Outflow
Journal article, 2025
Outflows are key indicators of ongoing star formation. We report the discovery of an unanchored forked stream within the propagating path of an extremely young protostellar outflow in the 70 μm-dark clump G34.74-0.12, based on Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm observations with an angular resolution of 1 . ″ 6 (∼5000 au). This outflow originates from a 9.7 M⊙ core, exhibits a fork-shaped stream structure in its redshifted lobe, which is traced by CO (2-1), SiO (5-4), and H2CO (30,3-20,2). It has a momentum of 13 M⊙ km s−1, an energy of 107 M⊙ km2 s−2, and a dynamical timescale of ∼104 yr. Significantly, the enhanced relative abundances of SiO, H2CO, and CH3OH with respect to CO, along with the increased temperature at the forked point, indicate a collisional origin. The forked point does not coincide with any dust continuum core >0.1 M⊙. Moreover, CO (2-1) emission also traces three other outflows in this region, characterized by their masses (0.40, 0.02, and 0.15 M⊙) and momenta (5.2, 0.2, and 1.8 M⊙ km s−1), as part of the ALMA Survey of 70 μm dark High-mass clumps in Early Stages project. All the newly discovered morphological and kinematic features associated with these extremely young protostellar outflows (with timescales of 103-104 yr) suggest that the initial stages of star formation are more complicated than previously understood.
Author
Shuting Lin
Xiamen University
S. Feng
Xiamen University
Patricio Sanhueza
University of Tokyo
Ke Wang
Beijing University of Technology
Z. Y. Zhang
Nanjing University
Yichen Zhang
Shanghai Jiao Tong University
Feng Wei Xu
Beijing University of Technology
Junzhi Wang
Guangxi University
Kaho Morii
Harvard-Smithsonian Center for Astrophysics
University of Tokyo
National Astronomical Observatory of Japan
Hauyu Baobab Liu
National Sun Yat-Sen University
National Taiwan Normal University
Sheng-Yuan Liu
Academia Sinica
Lile Wang
Beijing University of Technology
Hui Li
Tsinghua University
Daniel Tafoya
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Willem A. Baan
Netherlands Institute for Radio Astronomy (ASTRON)
Chinese Academy of Sciences
Shanghuo Li
Nanjing University
Giovanni Sabatini
Arcetri Astrophysical Observatory
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 990 2 229Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Astronomy, Astrophysics, and Cosmology
DOI
10.3847/1538-4357/adf208